What makes a plane go up?
What makes a plane go up? Air. A plane
flies through the air by continually pushing and pulling the surrounding air
downward. In response to the force of moving the air down, the air
pushes the airplane upward. Newton's 3rd law of motion states that for
every action there is an equal and opposite re-action. An airplane
wing is shaped so that the air is deflected downward as the wing passes.
Because air is a fluid (a gas), both the top and the bottom surface of the wing deflect the air.
This is very different than dealing with solid pellets for which only the bottom surface would deflect.
The faster an airplane travels the more lift is generated. Inclining
the wing to the wind also produces more deflection and more lift. The wings of an airplane
have adjustable flaps that can be extended or retracted. When
extended, the flaps increase the deflection of the air
and provide greater lift for takeoff and landing.
As it flies, a plane is in the center
of four forces. Lift (upward force) and thrust (forward push,
provided by a propeller) get a plane into the air. Gravity and
drag (air resistance, which is friction caused by air rubbing
against the plane) try to pull the plane down and slow its speed. A
plane must be built so that lift and thrust are stronger than the
pull of gravity and drag by just the right amount. Lift from the
wings is used to overcome the force of gravity. Shape is important in
overcoming drag. For example, the nose of a plane is
rounded so it can push through the air more easily. The front edge of
each wing is rounded too. An airplane built like a railroad boxcar
just wouldn't fly very well.
Return to Lesson #9